Zinc oxide, method for preparing the same, and use thereof

Abstract

The application discloses zinc oxide with specific crystal and microstructure, and belongs to the field of daily chemical raw materials. The zinc oxide disclosed by the application is in a hexagonal wurtzite crystal form, and can emit red light under 365 nm ultraviolet excitation. The surface of the zinc oxide has oxygen vacancies, and the density of the oxygen vacancies on the surface of the zinc oxide is 30-62%. The zinc oxide with the specific microstructure can not only shield ultraviolet rays, but also more importantly, can absorb ultraviolet rays and convert the ultraviolet rays into red light. No other metal ions are introduced into the zinc oxide, and the zinc oxide does not need to be compounded with other substances. The zinc oxide alone has ultraviolet light conversion performance, and provides a raw material selection with more outstanding sunscreen effect and higher safety for sunscreen products. Meanwhile, the application also discloses a preparation method of the zinc oxide and application of the zinc oxide in sunscreen products.

Description

Technical Field

[0001] This invention relates to an inorganic oxide, particularly a method for preparing zinc oxide, zinc oxide with a specific microstructure obtained by the method, and its application in daily chemical products. Background Technology

[0002] Zinc oxide is an inorganic compound widely used in sunscreen products as a UV-shielding ingredient. Beyond simply blocking UV rays, its ability to convert harmful UV light into beneficial light is a crucial area for advancement in this traditional sunscreen product.

[0003] Currently, the only commercially available zinc oxide with ultraviolet light conversion capability is the green fluorescent zinc oxide developed by Sakai Chemical Industry Co., Ltd. of Japan (see CN109415627A). This zinc oxide phosphor is prepared using a specific manufacturing method, which includes a mixing step of oxygen-containing zinc compounds and sulfur-containing compounds, followed by a calcination step of the resulting mixture. By incorporating sulfur and subjecting the mixture to high-temperature calcination, fluorescent zinc oxide capable of converting ultraviolet light into green fluorescence is obtained.

[0004] In addition, there are literature reports on the conversion of zinc oxide from ultraviolet light to red fluorescence by doping it with other metal ions or by mixing it with other substances. For example, CN 117228705 A discloses a method to achieve the simultaneous absorption of ultraviolet light and emission of red fluorescence by adjusting the ratio of zinc salt, non-zinc metal salt, and surfactant. CN117602663 A discloses the doping of zinc oxide with metal ions to change the crystal structure of ZnO, i.e., the vacancy and oxygen interstices, so that it can emit red fluorescence while absorbing ultraviolet light.

[0005] Therefore, to achieve the ultraviolet light conversion function of zinc oxide in the current technology, it is generally necessary to add other substances to it, and some preparation processes require high-temperature calcination. The following problems are common: (1) High-temperature calcination has high energy consumption, which seriously increases the preparation cost of zinc oxide; (2) Introducing other elements or compounding with other substances into zinc oxide does not result in pure zinc oxide products. The introduction of other elements or substances makes zinc oxide safe in subsequent applications, which seriously affects the widespread application of zinc oxide. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing zinc oxide with low energy consumption and without introducing other elements or substances, so that the prepared zinc oxide has ultraviolet light conversion function. Simultaneously, this invention also provides zinc oxide with a specific microstructure, ultraviolet light conversion function, and no safety issues. Furthermore, this invention provides applications of zinc oxide in daily chemical products such as sunscreens.

[0007] To achieve one of the above objectives, the present invention provides a zinc oxide with a specific microstructure, ultraviolet light conversion function, and no safety issues. The technical solution adopted is as follows: a zinc oxide, wherein the zinc oxide is hexagonal wurtzite crystal, which can emit red light under 365 nm ultraviolet excitation; the average particle size of the zinc oxide is 60-1000 nm; the surface of the zinc oxide has oxygen vacancies, and the density of oxygen vacancies on the surface of the zinc oxide is 30-62%.

[0008] The zinc oxide described in this invention has a hexagonal wurtzite crystal structure with an average particle size of 60-1000 nm and oxygen vacancies on its surface within a certain density range. This specific microstructure allows the zinc oxide to emit red light under 365 nm ultraviolet excitation, demonstrating ultraviolet light conversion capability. The inventors of this application discovered that the crystal structure, particle size range, and oxygen vacancies density of zinc oxide all directly affect its ultraviolet light conversion performance, with the oxygen vacancies density having a particularly significant impact.

[0009] The zinc oxide of this invention has an average particle size that can be any value or a range of any two values ​​selected from 60nm, 70nm, 80nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, and 1000nm. The density of oxygen holes on the surface of the zinc oxide can be any value or a range of any two values ​​selected from 30%, 32%, 35%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 56%, 58%, 60%, and 62%.

[0010] It should be noted that the average particle size of the zinc oxide described in this invention was obtained using dynamic light scattering (DLS). The oxygen hole density on the surface of the zinc oxide described in this invention was obtained by measuring the O1s energy spectrum data of the sample using X-ray photoelectron spectroscopy (XPS) and then performing peak segmentation.

[0011] Preferably, the average particle size of the zinc oxide is 60-500 nm.

[0012] Preferably, the oxygen vacancy density on the zinc oxide surface is 40-60%.

[0013] When the average particle size of the zinc oxide is 60-500 nm and the oxygen hole density on its surface is 40-60%, it can emit stronger red light after absorbing ultraviolet light and has more outstanding ultraviolet light conversion performance.

[0014] To achieve the aforementioned other objective, the present invention provides a method for preparing zinc oxide with low energy consumption and without introducing other elements or substances, thereby enabling the prepared zinc oxide to have ultraviolet light conversion function. The preparation method includes the following steps: (1) Add zinc salt solution, precipitant solution and cavitation aid into ultrasonic reactor, control the ultrasonic power of ultrasonic reactor to 100-2100W and the temperature to 10-100℃, and control the residence time of zinc salt solution, precipitant solution and cavitation aid in ultrasonic reactor to 10-300 seconds, and obtain product slurry after reaction; (2) After solid-liquid separation, washing and drying, the product slurry obtained in step (1) is used to obtain zinc oxide powder; the zinc oxide powder is added to a solvent to disperse it to obtain zinc oxide dispersion, and then a surface modifier is added to the zinc oxide dispersion for modification treatment to obtain modified slurry; (3) After solid-liquid separation, washing, drying, crushing and sieving of the modified slurry obtained in step (2), zinc oxide is obtained.

[0015] The zinc oxide preparation method of this invention involves the co-reaction of a zinc salt solution, a precipitant solution, and a cavitation aid in an ultrasonic reactor. By controlling the ultrasonic power, temperature, and residence time of the reactants within the reactor, the crystal structure, particle size, and surface oxygen vacancy density of the reaction products can be controlled, resulting in a product slurry with a specific microstructure. Furthermore, the obtained product slurry is modified with a surface modifier, which not only enhances the ultraviolet light conversion performance of zinc oxide but also solves problems such as uneven dispersion, poor compatibility, and skin irritation that zinc oxide may encounter in subsequent applications.

[0016] In a preferred embodiment of the zinc oxide preparation method of the present invention, the zinc salt solution in step (1) is at least one of zinc chloride aqueous solution, zinc nitrate aqueous solution, and zinc sulfate aqueous solution. The selection of the zinc salt solution in this application is not particularly limited; any zinc salt solution conventionally used in the preparation of zinc oxide in this field may be used, including but not limited to zinc chloride aqueous solution, zinc nitrate aqueous solution, and zinc sulfate aqueous solution.

[0017] In a preferred embodiment of the zinc oxide preparation method of the present invention, the precipitant solution in step (1) is a strong alkaline aqueous solution. The precipitant solution used in the zinc oxide preparation process of the present invention is not particularly limited; any precipitant solution conventionally used in the preparation of zinc oxide in the art can be used. A strong alkaline aqueous solution is preferred, for example, including but not limited to at least one of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution.

[0018] In a preferred embodiment of the zinc oxide preparation method of the present invention, the cavitation aid in step (1) is a volatile gas solution. The inventors of this application have discovered that during the reaction of zinc salt solution and precipitant solution in an ultrasonic reactor, the addition or absence of a cavitation aid has a significant impact on the microstructure of the prepared zinc oxide, especially on the cavitation structure on the zinc oxide surface. Selecting a suitable cavitation aid and an appropriate amount significantly affects the oxygen cavitation density on the surface of the prepared zinc oxide.

[0019] In a preferred embodiment of the zinc oxide preparation method of the present invention, the concentration of the zinc salt solution in step (1) is 0.5-4 mol / L. The zinc salt solution concentration used in the present invention is preferably 0.5-4 mol / L, for example, including but not limited to any value or a range of any two values ​​from 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, 2.5 mol / L, 2.6 mol / L, 2.8 mol / L, 3.0 mol / L, 3.4 mol / L, 3.6 mol / L, 3.8 mol / L, and 4.0 mol / L. More preferably, the concentration of the zinc salt solution is 1-3 mol / L.

[0020] In a preferred embodiment of the zinc oxide preparation method of the present invention, the concentration of the precipitant solution is 1-12 mol / L. The concentration of the precipitant solution used in the present invention is preferably 1-12 mol / L, for example, including but not limited to any value or a range of any two values ​​from 1 mol / L, 1.2 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L, 10 mol / L, 10.5 mol / L, 11 mol / L, 11.5 mol / L, and 12 mol / L. More preferably, the concentration of the precipitant solution is 4-8 mol / L.

[0021] In a preferred embodiment of the zinc oxide preparation method of the present invention, the cavitation aid is at least one selected from ammonia, aqueous carbon dioxide solution, and hydrochloric acid. The selection of the cavitation aid in this application has a certain influence on the microstructure of zinc oxide. Preferably, the cavitation aid is at least one selected from ammonia, aqueous carbon dioxide solution, and hydrochloric acid; more preferably, the cavitation aid is hydrochloric acid.

[0022] In a preferred embodiment of the zinc oxide preparation method of the present invention, the concentration of the cavitation aid is 0.5-2 mol / L. The concentration of the cavitation aid in this application has a certain influence on the microstructure of zinc oxide. The concentration of the cavitation aid is 0.5-2 mol / L, for example, including but not limited to any value or a range of any two values ​​from 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, and 2 mol / L. More preferably, the concentration of the cavitation aid is 0.8-1.2 mol / L.

[0023] In a preferred embodiment of the zinc oxide preparation method of the present invention, the flow rate ratio of the zinc salt solution, precipitant solution, and cavitation aid in step (1) is: zinc salt solution: precipitant solution: and cavitation aid = (0.1~2): (0.1~4): (0.01-0.3). During the preparation of zinc oxide according to the present invention, the flow rate ratio of the zinc salt solution, precipitant solution, and cavitation aid needs to be controlled within a certain range. If the flow rate ratio of the three is not appropriate, it will directly affect the zinc oxide formation rate or the microstructure of zinc oxide, especially the crystal form and surface oxygen vacancy density. The inventors of this application have found through research that only when the flow rate ratio of the three is controlled at (0.1~2): (0.1~4): (0.01-0.3) can the zinc oxide with a specific microstructure and good ultraviolet light conversion performance described in this application be prepared. The flow rate ratio of the zinc salt solution, precipitant solution, and cavitation aid can be, for example, 0.1:0.1:0.01, 0.1:0.1:0.05, 0.1:0.1:0.1, 0.1:0.1:0.2, 0.1:0.1:0.3, 0.5:0.8:0.01, 0.5:0.8:0.05, 0.5:0.8:0.1, or 0.5:0.8: The values ​​can be any point values ​​or a range of any two points selected from 0.2, 0.5:0.8:0.3, 1:1:0.01, 1:1:0.1, 1:1:0.2, 1:1:0.3, 1:2:0.01, 1:2:0.1, 1:2:0.2, 1:2:0.3, 1:3:0.01, 1:3:0.1, 1:3:0.2, 1:3:0.3, etc. More preferably, the flow rate ratio of the zinc salt solution, the precipitant solution, and the cavitation aid is 1:1:0.1.

[0024] In a preferred embodiment of the zinc oxide preparation method of the present invention, the ultrasonic power in step (1) is 100-1000W. The ultrasonic power in the ultrasonic reactor is one of the important parameters for regulating the reaction process of zinc salt solution and precipitant solution and the microstructure of product. The ultrasonic power directly affects the reaction rate, product yield, selectivity, by-product formation, crystal form, particle size and surface structure of zinc oxide by changing the intensity of cavitation effect, the number of cavitation bubbles and the collapse energy. The inventors of this application discovered that, considering the reaction materials and temperature conditions, the ultrasonic power needs to be controlled between 100-2100W to obtain zinc oxide with ultraviolet light conversion properties. For example, the ultrasonic power can be controlled at any point or any range of any two points from 100W, 150W, 200W, 300W, 400W, 500W, 600W, 700W, 800W, 900W, 1000W, 1100W, 1200W, 1300W, 1400W, 1500W, 1600W, 1700W, 1800W, 1900W, 2000W, and 2100W. Preferably, an ultrasonic power of 100-1000W yields zinc oxide with better ultraviolet light conversion properties. More preferably, an ultrasonic power of 600-1000W yields zinc oxide with even more superior ultraviolet light conversion properties.

[0025] In a preferred embodiment of the zinc oxide preparation method of the present invention, the temperature in the ultrasonic reactor in step (1) is 15-90℃. The temperature in the ultrasonic reactor is another key parameter for controlling the ultrasonic cavitation effect and reaction process. It can directly affect the yield, selectivity, morphology, size, and microstructure of the reaction products by changing the stability of the cavitation bubbles, their collapse energy, and reaction kinetics. The inventors of this application found in experiments that, combined with the reaction raw material system and other conditions of this application, the temperature in the ultrasonic reactor needs to be controlled at 10-100℃ to prepare zinc oxide with ultraviolet light conversion properties. The temperature in the ultrasonic reactor can be any point value or a range of any two points from 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, etc. Preferably, the temperature in the ultrasonic reactor is 15-90℃, resulting in zinc oxide with better ultraviolet light conversion performance. More preferably, the temperature in the ultrasonic reactor is 40-90℃, resulting in zinc oxide with even better ultraviolet light conversion performance.

[0026] In a preferred embodiment of the zinc oxide preparation method of the present invention, the residence time of the zinc salt solution, precipitant solution and cavitation aid in the ultrasonic reactor in step (1) is 60-200 seconds. The residence time of the reactants in the ultrasonic reactor is another key parameter for controlling the reaction process and product characteristics. The length of the residence time can change the duration of interaction between the reactants and the ultrasonic cavitation effect, the conversion rate of reactants, the probability of secondary reaction of products, etc., thereby affecting the yield, selectivity, purity and microstructure (particle size, morphology, surface structure, etc.) of the product. The inventors of this application conducted repeated experimental studies, and combined the reaction raw material system, ultrasonic power, and temperature selection described in this application, ultimately discovered that a residence time of 10-300 seconds for the zinc salt solution, precipitant solution, and cavitation aid in the ultrasonic reactor can prepare zinc oxide with good ultraviolet light conversion performance. If the residence time is too short, the reactants do not have sufficient residence time in the ultrasonic region, and only some molecules are activated by the cavitation effect. For example, chemical bonds are not fully broken, and reactants are not fully mixed, resulting in low reaction conversion rate, low product yield, and the inability to form zinc oxide with a specific microstructure, thus failing to convert ultraviolet light into red light. Conversely, if the residence time is too long, the already formed target product will continue to be exposed to the cavitation effect, which may lead to "secondary reactions" (such as decomposition, polymerization, and oxidation). This not only reduces product purity and selectivity but also increases the particle size of zinc oxide and affects the surface oxygen vacancy density, also preventing the formed zinc oxide from converting ultraviolet light into red light. Therefore, the residence time of the zinc salt solution, precipitant solution, and cavitation aid in the ultrasonic reactor includes, but is not limited to, any point value or a range of any two points from 10s, 20s, 50s, 60s, 80s, 100s, 150s, 200s, 250s, and 300s. Preferably, the residence time of the zinc salt solution, precipitant solution, and cavitation aid in the ultrasonic reactor is 60-200 seconds, resulting in zinc oxide with better size and surface oxygen cavities, and better ultraviolet light conversion performance. More preferably, the residence time of the zinc salt solution, precipitant solution, and cavitation aid in the ultrasonic reactor is 80-200 seconds, resulting in zinc oxide with the best ultraviolet light conversion performance.

[0027] The ultrasonic pressure, temperature, and residence time of the zinc salt solution, precipitant solution, and cavitation aid in the ultrasonic reactor are related. Only through proper selection and combination of these three factors can the specific crystal and microstructure of zinc oxide described in this invention be obtained. Specifically, when the ultrasonic pressure in the ultrasonic reactor is 100-500 W, the temperature needs to be 40-100℃, and the residence time of the zinc salt solution, precipitant solution, and cavitation aid in the ultrasonic reactor needs to reach 60-300 s to ensure that the microstructure of the prepared zinc oxide achieves a specific average particle size and a specific oxygen vacancy density.

[0028] Preferably, when the ultrasonic pressure in the ultrasonic reactor is 100-500W, the temperature in the ultrasonic reactor needs to be selected as 40-90℃, and the residence time of the zinc salt solution, precipitant solution and cavitation aid in the ultrasonic reactor reaches 80-200s, the ultraviolet light conversion performance of the prepared zinc oxide is better.

[0029] When the ultrasonic pressure in the ultrasonic reactor is 600-2100W, the temperature in the ultrasonic reactor is selected to be 15-40℃, and the residence time of the zinc salt solution, precipitant solution and cavitation aid in the ultrasonic reactor is 80-300s, the microstructure of the prepared zinc oxide can achieve a specific average particle size and a specific oxygen vacancy density.

[0030] When the ultrasonic pressure in the ultrasonic reactor is 100-500W and the temperature is 40-100℃, or when the ultrasonic pressure in the ultrasonic reactor is 600-2100W and the temperature is 15-40℃, and the residence time of the zinc salt solution, precipitant solution and cavitation aid in the ultrasonic reactor is 10-300s, zinc oxide with the specific crystal and microstructure can be prepared.

[0031] In step (1), the zinc salt solution, precipitant solution, and cavitation aid can be added to the ultrasonic reactor simultaneously. Generally, the three materials are pumped into the ultrasonic reactor. There are no special requirements for the type of pump; common pumps used for material transport, such as centrifugal pumps, plunger pumps, and peristaltic pumps, can be used. The pump flow rate depends on the size of the ultrasonic reactor used. The pump flow rate mainly affects the residence time of the materials inside the ultrasonic reactor. There are no special requirements for the volume of the ultrasonic reactor. The volume of the ultrasonic reactor and the pump flow rate should be coordinated to ensure that the residence time of the three materials inside the reactor reaches the required range.

[0032] It should be noted that in step (1), the residence time of the zinc salt solution, precipitant solution and cavitation aid in the ultrasonic reactor is the volume of the ultrasonic reactor divided by the total flow rate of the three materials, namely, the residence time is the volume of the ultrasonic reactor divided by the sum of the flow rates of the three materials.

[0033] In step (1), there is no strict requirement for the order of adding zinc salt solution, precipitant solution and cavitation aid. The zinc salt solution feed pump or precipitant solution feed pump can be turned on first, and then the cavitation aid feed pump can be turned on in sequence; or the zinc salt solution, precipitant solution and cavitation aid can be fed into the ultrasonic reactor at the same time.

[0034] In the zinc oxide preparation method of the present invention, step (2) involves solid-liquid separation of the product slurry and washing and drying to obtain zinc oxide powder. Then, the zinc oxide powder needs to be added to a solvent to prepare a zinc oxide dispersion. The mass concentration of the zinc oxide dispersion is preferably 5-40%. If the concentration exceeds 40%, the content will be difficult to stir into clumps, affecting the uniformity of the modification. The solvent can be, for example, an aqueous ethanol solution. The mass fraction of ethanol in the aqueous ethanol solution can be 30-80%, for example, including but not limited to any point value or any range of two points from 30%, 40%, 50%, 60%, 70%, 80%.

[0035] In a preferred embodiment of the zinc oxide preparation method of the present invention, the surface modifier in step (2) is a silane coupling agent. In the zinc oxide preparation method of the present application, after the zinc salt solution, precipitant solution and cavitation aid undergo a specific reaction in an ultrasonic reactor, the resulting product needs to be further modified. This not only further modifies the size and microstructure of zinc oxide, thus improving its ultraviolet light conversion performance, but also further improves its dispersion uniformity, compatibility, and safety for use in the daily chemical industry. The surface modifier is preferably a silane coupling agent, such as n-octyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane (KH-570), octyltrimethoxysilane (KH-832), dodecyltrimethoxysilane (DTS), etc.

[0036] In a preferred embodiment of the zinc oxide preparation method of the present invention, the amount of surface modifier used in step (2) is 3-20% of the mass of the zinc oxide dispersion. For the zinc oxide with the structure prepared in this application, the amount of surface modifier added during surface modification determines the modification effect. If the amount added is too small, the surface modification of zinc oxide will be insufficient, the optimization of ultraviolet light conversion performance will be insignificant, and problems such as agglomeration and poor compatibility will still exist in subsequent use. If the amount of surface modifier added is too large, it will not only waste the surface modifier and increase side reactions, but also damage the surface microstructure of zinc oxide. This will not only fail to further optimize and improve the ultraviolet light conversion performance of zinc oxide, but will also have an adverse effect on the ultraviolet light conversion performance of zinc oxide, and will also cause problems such as poor skin feel when subsequently applied to daily chemical products. Through repeated experiments, the inventors of this application discovered that using a surface modifier at 3-20% of the zinc oxide dispersion not only further optimizes and improves the ultraviolet light conversion performance of zinc oxide, but also significantly improves the dispersion uniformity and compatibility of the modified zinc oxide. The amount of the surface modifier can be, for example, any value or a range of any two values ​​from 3%, 5%, 6%, 8%, 9%, 10%, 12%, 15%, 16%, 18%, and 20% of the zinc oxide dispersion. Preferably, using a surface modifier at 3-10% of the zinc oxide dispersion allows the modified zinc oxide to better balance excellent ultraviolet light conversion performance with good dispersion uniformity and compatibility, resulting in a superior modification effect.

[0037] The surface modifier is added to the zinc oxide dispersion in step (2), and the reaction needs to be carried out at a certain temperature. The reaction temperature is 40-90℃, including but not limited to any point value or any range of two points from 40℃, 50℃, 60℃, 70℃, 80℃, and 90℃. The reaction time is 2-9 hours, including but not limited to any point value or any range of two points from 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, and 9 hours.

[0038] In the zinc oxide preparation method of the present invention, the solid-liquid separation of the modified slurry in step (3) can be performed using conventional methods in the art, such as centrifugation and filtration. After solid-liquid separation in step (3), the slurry is washed clean and dried to obtain powder. The drying temperature is generally 60-120℃, including but not limited to any point value or any range of two points such as 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, and 120℃. The powder obtained after drying is crushed and sieved to obtain the zinc oxide of the present invention.

[0039] To achieve another objective mentioned above, this invention provides an application of zinc oxide as described above in sunscreen products. The zinc oxide of this invention is prepared using a specific method, and possesses a specific crystal structure and size range. Its surface has oxygen vacancies within a certain density range, exhibiting excellent ultraviolet light conversion properties. Under 365 nm ultraviolet excitation, it emits red light, demonstrating good sun protection effects and providing a new material option for sunscreen products.

[0040] Finally, the present invention also provides a sunscreen product containing zinc oxide as described above. The sunscreen product of the present invention contains zinc oxide with ultraviolet light conversion properties as described above. This zinc oxide not only blocks ultraviolet rays but also absorbs ultraviolet light and converts it into red light. Furthermore, the zinc oxide does not contain other elements or is not compounded with other substances, thus possessing not only excellent sun protection effects but also good safety.

[0041] In the sunscreen product described in this invention, the amount of zinc oxide added is not particularly limited. For example, it can be 1-25%. 25% is the maximum amount added as specified in China's "Cosmetic Safety Technical Specifications". It includes, but is not limited to, any point value or any range of two points from 1%, 2%, 3%, 5%, 6%, 8%, 10%, 12%, 15%, 16%, 17%, 18%, 20%, 25%.

[0042] The sunscreen product described in this invention also contains other substances that can be added to the sunscreen product, such as, but not limited to, preservatives, antioxidants, pH adjusters, fragrances, and pigments.

[0043] The zinc oxide described in this invention has a specific average particle size range, exhibiting a hexagonal wurtzite crystal form and a certain density of oxygen vacancies on its surface. It emits red light under 365 nm ultraviolet excitation. This zinc oxide with its specific microstructure not only shields against ultraviolet light but, more importantly, can absorb ultraviolet light and convert it into red light. No other metal ions are introduced into this zinc oxide, and it does not require compounding with other substances. This zinc oxide alone possesses ultraviolet light conversion properties, providing sunscreen products with a zinc oxide option that offers superior sun protection and enhanced safety.

[0044] The zinc oxide preparation method of this invention starts from the microstructure and crystal structure of zinc oxide. A cavitation aid is added to an ultrasonic reactor and reacted together with a zinc salt solution and a precipitant solution. By controlling the ultrasonic power, temperature, and residence time of the three materials in the ultrasonic reactor, a large number of microjets are generated using the ultrasonic cavitation effect to impact the surface of the zinc oxide crystals, forming numerous oxygen vacancies. This achieves surface microstructure adjustment of the pure zinc oxide crystals, resulting in zinc oxide with a specific microstructure and good ultraviolet light conversion performance. The preparation method uses continuous flow synthesis, does not require high-temperature calcination, has the advantage of low energy consumption, and produces a pure zinc oxide product with special fluorescence properties.

[0045] The application of zinc oxide in sunscreen products described in this invention, and the sunscreen products containing zinc oxide described in this invention, provide new raw material options and safer sunscreen products with unique UV protection properties for the sunscreen daily chemical industry. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the zinc oxide preparation process described in this invention.

[0047] Figure 2 The images show SEM images of zinc oxide prepared by different ultrasonic reaction temperatures according to the present invention.

[0048] Figure 3 The image shows a SEM image of the zinc oxide prepared in Example 1.

[0049] Figure 4 This is a SEM image of the zinc oxide prepared in Example 2.

[0050] Figure 5 This is a SEM image of the zinc oxide prepared in Example 3.

[0051] Figure 6 The image shows the excitation spectrum of the zinc oxide prepared in Example 1.

[0052] Figure 7 The emission spectrum and optical image of the zinc oxide prepared in Example 1 when excited at a UV wavelength of 365 nm.

[0053] Figure 8 The XPS spectrum of zinc oxide prepared in Example 1 is shown.

[0054] Figure 9 An optical image of the zinc oxide prepared for Comparative Example 1 excited at a UV wavelength of 365 nm.

[0055] Figure 10 An optical image of the zinc oxide prepared in Comparative Example 2, excited at a wavelength of 365 nm ultraviolet light.

[0056] Figure 11 An optical image of the zinc oxide prepared in Comparative Example 3 excited at a UV wavelength of 365 nm.

[0057] Figure 12 The XRD patterns of zinc oxide obtained before and after modification are shown.

[0058] Figure 13 The images show the appearance and characteristics of the sunscreen lotion without zinc oxide and those with zinc oxide added in Example 1 and Comparative Example 1, respectively, under 365nm ultraviolet light irradiation. Detailed Implementation

[0059] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0060] All raw materials used in the following examples are substances that can be obtained by conventional preparation methods or conventional channels in the art.

[0061] Example 1 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A 2 mol / L zinc nitrate aqueous solution, a 4 mol / L sodium hydroxide solution, and a 1 mol / L hydrochloric acid solution were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid was 1:1:0.1. The ultrasonic power of the ultrasonic reactor was controlled at 600W and the temperature at 80℃. The residence time of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid in the ultrasonic reactor was controlled at 200 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 30%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 5% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0062] Example 2 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A 2 mol / L zinc nitrate aqueous solution, a 4 mol / L sodium hydroxide solution, and a 1 mol / L hydrochloric acid solution were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid was 1:1:0.1. The ultrasonic power of the ultrasonic reactor was controlled at 600W and the temperature at 10℃. The residence time of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid in the ultrasonic reactor was controlled at 300 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (ethanol mass fraction is 50%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 5% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0063] Example 3 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A 2 mol / L zinc nitrate aqueous solution, a 4 mol / L sodium hydroxide solution, and a 1 mol / L hydrochloric acid solution were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid was 1:1:0.1. The ultrasonic power of the ultrasonic reactor was controlled at 300W and the temperature at 80℃. The residence time of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid in the ultrasonic reactor was controlled at 120 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 80%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 5% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0064] Example 4 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) First, turn on the zinc salt solution delivery pump and add a 0.5 mol / L zinc chloride aqueous solution to the ultrasonic reactor. Then, turn on the delivery pumps of the precipitant solution and cavitation aid at the same time and add a 1 mol / L potassium hydroxide solution and a 0.5 mol / L ammonia solution to the ultrasonic reactor at the same time. The flow rate ratio of zinc chloride aqueous solution, potassium hydroxide solution and ammonia solution is 0.1:1:0.3. Control the ultrasonic power of the ultrasonic reactor to 100W and the temperature to 15℃. Control the residence time of zinc chloride aqueous solution, potassium hydroxide solution and ammonia solution in the ultrasonic reactor to 250 seconds. After the reaction, the product slurry is obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 30%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 8% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 90°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0065] Example 5 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A zinc sulfate aqueous solution with a concentration of 4 mol / L, a potassium hydroxide solution with a concentration of 3 mol / L, and a carbon dioxide aqueous solution with a concentration of 2 mol / L were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc sulfate aqueous solution, potassium hydroxide solution, and carbon dioxide aqueous solution was 2:0.1:0.2. The ultrasonic power of the ultrasonic reactor was controlled at 1000W and the temperature at 25℃. The residence time of the zinc sulfate aqueous solution, potassium hydroxide solution, and carbon dioxide aqueous solution in the ultrasonic reactor was controlled at 60 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 60%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 12% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0066] Example 6 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A 1 mol / L zinc chloride aqueous solution, a 10 mol / L potassium hydroxide solution, and a 1 mol / L ammonia solution were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc chloride aqueous solution, potassium hydroxide solution, and ammonia solution was 1:1:0.1. The ultrasonic power of the ultrasonic reactor was controlled at 1500W and the temperature at 30℃. The residence time of the zinc chloride aqueous solution, potassium hydroxide solution, and ammonia solution in the ultrasonic reactor was controlled at 80 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 80%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 15% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0067] Example 7 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A 3 mol / L zinc chloride aqueous solution, an 8 mol / L potassium hydroxide solution, and a 0.8 mol / L hydrochloric acid were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc chloride aqueous solution, potassium hydroxide solution, and hydrochloric acid was 1:1:0.1. The ultrasonic power of the ultrasonic reactor was controlled at 500W and the temperature at 40℃. The residence time of the zinc chloride aqueous solution, potassium hydroxide solution, and ammonia in the ultrasonic reactor was controlled at 150 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 80%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 3% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0068] Example 8 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A 2 mol / L zinc nitrate aqueous solution, a 6 mol / L sodium hydroxide solution, and a 1.2 mol / L hydrochloric acid were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid was 1:2:0.05. The ultrasonic power of the ultrasonic reactor was controlled at 800W and the temperature at 90℃. The residence time of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid in the ultrasonic reactor was controlled at 100 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 30%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 10% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0069] Example 9 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A 3 mol / L zinc nitrate aqueous solution, a 12 mol / L sodium hydroxide solution, and a 1.5 mol / L carbon dioxide aqueous solution were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc nitrate aqueous solution, sodium hydroxide solution, and carbon dioxide aqueous solution was 1:3:0.3. The ultrasonic power of the ultrasonic reactor was controlled at 2000W and the temperature at 100℃. The residence time of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid in the ultrasonic reactor was controlled at 10 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 60%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 20% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0070] Example 10 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A 2 mol / L zinc nitrate aqueous solution, a 4 mol / L sodium hydroxide solution, and a 1 mol / L hydrochloric acid solution were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid was 1:1:0.1. The ultrasonic power of the ultrasonic reactor was controlled at 2100W and the temperature at 80℃. The residence time of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid in the ultrasonic reactor was controlled at 50 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 60%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 5% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0071] Example 11 One embodiment of the zinc oxide of the present invention is illustrated in the attached diagram, which shows the preparation process of the zinc oxide in this embodiment. Figure 1 As shown, the specific steps include: (1) A 2 mol / L zinc nitrate aqueous solution, a 4 mol / L sodium hydroxide solution, and a 1 mol / L hydrochloric acid solution were simultaneously added to an ultrasonic reactor. The flow rate ratio of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid was 1:1:4. The ultrasonic power of the ultrasonic reactor was controlled at 600W and the temperature at 80℃. The residence time of the zinc nitrate aqueous solution, sodium hydroxide solution, and hydrochloric acid in the ultrasonic reactor was controlled at 200 seconds. After the reaction, a product slurry was obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 60%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 5% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) The modified slurry obtained in step (2) is centrifuged for solid-liquid separation, washed and dried at a drying temperature of 80°C. After crushing and sieving, zinc oxide of this embodiment is obtained.

[0072] Comparative Example 1 This invention provides a comparative example of zinc oxide preparation. The method for preparing zinc oxide in this comparative example differs from Example 1 only in the ultrasonic power within the ultrasonic reactor; all other aspects are identical to Example 1. In the zinc oxide preparation process described in this comparative example, the ultrasonic power in the ultrasonic reactor is 0W.

[0073] Comparative Example 2 This invention provides a comparative example of zinc oxide. The preparation method of zinc oxide described in this comparative example differs from that in Example 1 only in that hydrochloric acid is not added in step (1), and the flow rate ratio of zinc nitrate aqueous solution to sodium hydroxide solution is 1:1. All other aspects are the same as in Example 1.

[0074] Comparative Example 3 This invention provides a comparative example of zinc oxide. The preparation method of zinc oxide described in this comparative example differs from that in Example 4 only in that ammonia is not added in step (1), and the flow rate ratio of zinc chloride aqueous solution to potassium hydroxide solution is 0.1:1. All other aspects are the same as in Example 4.

[0075] Comparative Example 4 This invention provides a comparative example of the zinc oxide preparation method. The only difference between this comparative example and Example 1 is the temperature in the ultrasonic reactor during step (1); all other aspects are the same as in Example 1. In this comparative example, the temperature in the ultrasonic reactor during step (1) is 110°C.

[0076] Example 1 The zinc oxide prepared in Examples 1-11 and Comparative Examples 1-3 (the zinc oxide preparation method in Comparative Example 4 failed to produce zinc oxide due to boiling caused by excessively high temperature in the ultrasonic reactor, so it was not tested) was subjected to tests for crystal morphology, average particle size, oxygen hole density, and optical properties. The test methods are as follows: Crystal morphology: The crystal structure of each group of zinc oxide was tested by X-ray diffraction (XRD). Average particle size: The average particle size of zinc oxide in each group was measured using scanning electron microscopy (SEM statistical method). Oxygen hole density: Obtained by peak splitting after measuring the O1s energy spectrum data of the sample using X-ray photoelectron spectroscopy (XPS).

[0077] Optical performance test: Irradiate the sample powder with ultraviolet light at a wavelength of 365nm in a dark room and observe the sample state.

[0078] The test results for each group are shown in Table 1 below.

[0079] Example 1 Hexagonal wurtzite crystal form 60 nm 44.6% It emits strong red light when excited by 365 nm ultraviolet light. Example 2 Hexagonal wurtzite crystal form 1μm 33.2% It emits red light when excited by 365 nm ultraviolet light. Example 3 Hexagonal wurtzite crystal form 1μm 40.1% It emits red light under 365 nm ultraviolet excitation. Example 4 Hexagonal wurtzite crystal form 200 nm 30.2% It emits red light when excited by 365 nm ultraviolet light. Example 5 Hexagonal wurtzite crystal form 80 nm 45% It emits strong red light when excited by 365 nm ultraviolet light. Example 6 Hexagonal wurtzite crystal form 62 nm 52.3% It emits strong red light when excited by 365 nm ultraviolet light. Example 7 Hexagonal wurtzite crystal form 200 nm 46.5% It emits strong red light when excited by 365 nm ultraviolet light. Example 8 Hexagonal wurtzite crystal form 500 nm 56.9% It emits strong red light when excited by 365 nm ultraviolet light. Example 9 Hexagonal wurtzite crystal form 320 nm 60.8% It emits red light when excited by 365 nm ultraviolet light. Example 10 Hexagonal wurtzite crystal form 60 nm 50% It emits red light when excited by 365 nm ultraviolet light. Example 11 Hexagonal wurtzite crystal form 80 nm 52% It emits red light under 365 nm ultraviolet excitation. Comparative Example 1 Hexagonal wurtzite crystal form 5μm 37.7% It did not emit red light under 365 nm ultraviolet excitation. Comparative Example 2 Hexagonal wurtzite crystal form 1μm 40% It did not emit red light under 365 nm ultraviolet excitation. Comparative Example 3 Hexagonal wurtzite crystal form 2 μm 35% It did not emit red light under 365 nm ultraviolet excitation. As can be seen from the comparison between Example 1 and Examples 2-3 in Table 1, the differences between Examples 2 and 3 and Example 1 are the temperature and ultrasonic power in the ultrasonic reactor. According to the test results of Examples 1-3 in Table 1, the temperature and ultrasonic power in the ultrasonic reactor have a direct impact on the particle size and oxygen vacancy density of the prepared zinc oxide. Compared with Example 1, the average particle size of the prepared zinc oxide in Examples 2-3 is significantly increased.

[0080] Under the same crystal structure, the ultraviolet light conversion performance of zinc oxide is directly related to its average particle size and oxygen hole density. To achieve more significant ultraviolet light conversion performance, it is necessary to take into account both the appropriate average particle size and oxygen hole density. The zinc oxide prepared in Examples 1 and 5-8 emits stronger red light under 365 nm ultraviolet excitation, indicating that the zinc oxide prepared in these examples has better ultraviolet light conversion performance. It also shows that when the average particle size of zinc oxide is 60-500 nm and the oxygen hole density is 40-60%, its ultraviolet light absorption and conversion performance is more excellent.

[0081] A comparison of Example 1 and Example 11 shows that the only difference between Example 1 and Example 1 is the flow rate ratio of the zinc salt solution, precipitant solution, and cavitation aid. The flow rate ratio of the cavitation aid is significantly increased. As shown in Table 1, the average particle size, oxygen hole density, and fluorescence properties of the zinc oxide prepared in Example 1 and Example 11 are significantly different. Specifically, the average particle size and oxygen hole density of the zinc oxide in Example 11 are higher than those in Example 1, but the intensity of the red light emitted under 365 nm ultraviolet excitation is not as high as that in Example 1. This indicates that the average particle size and oxygen hole density of zinc oxide are not necessarily better the higher they are, and there is no positive correlation between the average particle size and oxygen hole density of zinc oxide and its absorption and conversion performance of ultraviolet light.

[0082] As can be seen from the comparison between Example 1 and Comparative Example 1, the ultrasonic power in the ultrasonic reactor has a direct impact on the average particle size and oxygen vacancy density of the prepared zinc oxide, especially the average particle size of zinc oxide. The average particle size of the zinc oxide obtained in Comparative Example 1 is as high as 5 μm, which not only does not have the performance of ultraviolet light conversion, but also is not conducive to its subsequent application in daily chemical products due to its large size.

[0083] As can be seen from the comparison between Example 1 and Comparative Examples 2 and 3, the addition of cavitation aid also has a certain influence on the average particle size and oxygen hole density of the prepared zinc oxide. Under the same conditions, the addition of cavitation aid can regulate the average particle size of zinc oxide and the oxygen hole density formed on its surface, thereby changing the fluorescence properties of the prepared zinc oxide.

[0084] Example 2 Experiment on the effect of temperature in the ultrasonic reactor on the microstructure of the prepared zinc oxide This example mainly investigates the effect of temperature change in the ultrasonic reactor on the microstructure of the prepared zinc oxide. Four different ultrasonic reaction temperatures were set in this example: 10℃, 40℃, 60℃ and 90℃. Except for the temperature in the ultrasonic reactor, all other conditions were the same in the four different methods.

[0085] The preparation methods of the four groups of zinc oxide include the following steps: (1) Add 2 mol / L zinc nitrate aqueous solution, 4 mol / L sodium hydroxide solution and 1 mol / L hydrochloric acid to the ultrasonic reactor at the same time. The flow rate ratio of zinc nitrate aqueous solution, sodium hydroxide solution and hydrochloric acid is 1:1:0.1. Control the ultrasonic power of the ultrasonic reactor to 600W and the temperature to 10℃, 40℃, 60℃ or 90℃ respectively. Control the residence time of zinc nitrate aqueous solution, sodium hydroxide solution and hydrochloric acid in the ultrasonic reactor to 200 seconds. After the reaction, the product slurry is obtained. (2) The product slurry obtained in step (1) is centrifuged to separate solid and liquid, washed and dried to obtain zinc oxide powder; the zinc oxide powder is added to ethanol (the mass fraction of ethanol is 30%) to disperse to obtain zinc oxide dispersion, and then silane coupling agent n-octyltriethoxysilane is added to the zinc oxide dispersion. The amount of silane coupling agent added is 5% of the zinc oxide dispersion. The mixture is stirred evenly and modified at 90°C for 2 hours to obtain modified slurry. (3) Centrifuge the modified slurry obtained in step (2) to separate solid and liquid, wash and dry it at a drying temperature of 80°C. After crushing and sieving, four groups of zinc oxide are obtained.

[0086] The particle size of the four groups of zinc oxide prepared was measured by scanning electron microscopy (SEM). SEM images of the zinc oxide prepared at different temperatures are attached. Figure 2 As shown.

[0087] From the appendix Figure 2It can be seen that the reaction temperature has a significant impact on the morphology and structure of the product. With increasing temperature, the obtained zinc oxide product gradually transforms from a loose structure with a clearly regular morphology into a dense aggregate of particles. This may be because increasing the temperature accelerates the reaction rate, affecting the nucleation and growth process of the crystals, thus altering the growth mode and final morphology of the product. The inventors tested the fluorescence properties of each group of products and found that, under the same conditions, zinc oxide prepared in an ultrasonic reactor at temperatures of 40-90℃ exhibited better ultraviolet light conversion performance.

[0088] In addition, the particle size of the zinc oxide prepared in Examples 1, 2, and 3 was measured using scanning electron microscopy (SEM), and the results are shown in the attached figure. Figure 3-5 As shown.

[0089] From the appendix Figure 3 It can be seen that the average particle size of the zinc oxide prepared in Example 1 is 60 nm. (From the attached...) Figure 4 and 5 It can be seen that in Examples 2 and 3, due to the lower temperature or lower power in the ultrasonic reactor, the average particle size of the prepared zinc oxide was significantly increased, with an average particle size of 1 μm in both cases.

[0090] Example 3 Ultraviolet light conversion performance test of zinc oxide described in this invention The maximum absorption wavelength and the corresponding photoluminescence (PL) spectrum of zinc oxide were measured using a transient steady-state fluorescence spectrometer. The excitation spectrum and emission spectrum of zinc oxide prepared in Example 1, excited at 365 nm ultraviolet wavelength, were also measured, along with optical images. The test results are shown in the attached figures. Figure 6 and 7 As shown.

[0091] From the appendix Figure 6 and 7 It can be seen that the zinc oxide prepared in Example 1 can effectively absorb light in the 250 nm-450 nm wavelength range. The absorption peak is at 365 nm. It can emit strong red light under 365 nm ultraviolet excitation.

[0092] The surface oxygen vacancies of the zinc oxide obtained in Example 1 were measured using X-ray photoelectron spectroscopy (XPS), and the resulting XPS spectra are shown in the attached figure. Figure 8 As shown. (From the appendix) Figure 8 It can be seen that there are many oxygen vacancies on the surface of the zinc oxide prepared in Example 1.

[0093] Meanwhile, the optical properties of zinc oxide prepared in Comparative Examples 1, 2, and 3 under 365 nm ultraviolet light excitation were tested respectively, and the test results are shown in the appendix. Figure 9-11 As shown. (From the appendix) Figure 9-11It can be seen that the zinc oxide prepared in Comparative Examples 1-3 did not emit red light when excited at a UV wavelength of 365 nm.

[0094] Example of effect 4 Experimental study on the effect of surface modification on the microstructure of the zinc oxide prepared by the zinc oxide preparation method of the present invention. This example sets up two groups as test groups, namely the unmodified group and the modified group. The modified group uses the same method as in Example 1 to prepare zinc oxide. The unmodified group is different from Example 1 only in that it does not contain step (2) in Example 1.

[0095] The crystal structure of the two groups of zinc oxides was determined by X-ray diffraction (XRD). The XRD patterns of the two groups of zinc oxides are shown in the attached figures. Figure 12 As shown.

[0096] From the appendix Figure 12 As can be seen, the positions and intensities of the peaks in the XRD patterns of the modified zinc oxide and the unmodified zinc oxide are significantly different. The intensity of some diffraction peaks in the modified zinc oxide is significantly enhanced, indicating that the crystallinity of the modified zinc oxide may be improved and the crystal structure is more regular. At the same time, some new diffraction peaks appeared in the modified zinc oxide, or the relative intensities of the original peaks changed significantly, indicating that the phase ratio and microstructure of the modified zinc oxide were changed, thus affecting the crystal structure characteristics of zinc oxide.

[0097] Example 5 Effect test of the zinc oxide prepared into sunscreen product according to the present invention This example examines the sun protection effect of the sunscreen lotion product prepared from zinc oxide according to the present invention. This example includes a blank group, an experimental group, and a control group.

[0098] The sunscreen in the experimental group contained zinc oxide prepared in Example 1, specifically containing the following ingredients by weight percentage: cetearyl glucoside 2.2%, PEG-100 glyceryl stearate 0.8%, cetearyl alcohol 1%, hydrogenated polydecene 4%, jojoba oil 3%, squalane 3%, polydimethylsiloxane 3%, shea butter 2%, 2,6-di-tert-butyl-p-phenol 0.1%, SEPPLUS 400 (polyacrylate-13, polyisobutylene, polysorbate-20) 0.4%, propylparaben 0.1%, zinc oxide prepared in Example 1 3%, EDTA-2Na 0.05%, Glycerin 5%, Butylene Glycol 2%, Sodium Hyaluronate 0.03%, Betaine 1%, Sodium Stearoyl Glutamate 0.2%, Methylparaben 0.2%, Allantoin 0.15%, D-Panthenol 0.5%, Phenoxyethanol 0.4%, Ethylhexylglycerin 0.05%, Water balance.

[0099] The only difference between the blank group and the experimental group was that the blank group did not contain zinc oxide, which was present in the experimental group.

[0100] The control group differed from the experimental group only in that the zinc oxide prepared in Comparative Example 2 was used instead of the zinc oxide prepared in Example 1.

[0101] The appearance of the sunscreen products in the blank group, experimental group, and control group were observed and compared under 365nm ultraviolet light irradiation. The results are shown in the attached figure. Figure 13 As shown.

[0102] From the appendix Figure 13 As can be seen, the sunscreen containing the zinc oxide of this invention emits red light under 365 nm ultraviolet irradiation, while the blank group without added zinc oxide shows no obvious fluorescence reaction under 365 nm ultraviolet light irradiation, and the control group containing the zinc oxide described in Comparative Example 2 exhibits purple fluorescence at 365 nm. This demonstrates that the zinc oxide described in this invention has unique fluorescence characteristics, possessing the property of absorbing ultraviolet light and converting it into red light.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing zinc oxide, characterized in that, The preparation method includes the following steps: (1) Add zinc salt solution, precipitant solution and cavitation aid to ultrasonic reactor respectively. The flow rate ratio of zinc salt solution, precipitant solution and cavitation aid is: zinc salt solution: precipitant solution: cavitation aid = (0.1~2): (0.1~4): (0.01-0.3). Control the ultrasonic power of ultrasonic reactor to 100-2100W and the temperature to 10-100℃. Control the residence time of zinc salt solution, precipitant solution and cavitation aid in ultrasonic reactor to 10-300 seconds. After the reaction, the product slurry is obtained. (2) After solid-liquid separation, washing and drying, the product slurry obtained in step (1) is used to obtain zinc oxide powder; the zinc oxide powder is added to a solvent to disperse it to obtain zinc oxide dispersion, and then a surface modifier is added to the zinc oxide dispersion for modification treatment to obtain modified slurry; (3) After solid-liquid separation, washing, drying, crushing and sieving of the modified slurry obtained in step (2), zinc oxide is obtained.

2. The method for preparing zinc oxide as described in claim 1, characterized in that, The zinc salt solution in step (1) is at least one of zinc chloride aqueous solution, zinc nitrate aqueous solution, and zinc sulfate aqueous solution; And / or, the precipitant solution in step (1) is a strong alkaline aqueous solution; And / or, in step (1), the cavitation aid is an aqueous solution of a volatile gas.

3. The method for preparing zinc oxide as described in claim 1 or 2, characterized in that, The concentration of the zinc salt solution in step (1) is 0.5-4 mol / L; And / or, the precipitant solution is at least one of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution; And / or, the concentration of the precipitant solution is 1-12 mol / L; And / or, the cavitation aid is at least one of ammonia, aqueous carbon dioxide solution, and hydrochloric acid; And / or, the concentration of the cavitation aid is 0.5-2 mol / L.

4. The method for preparing zinc oxide as described in claim 1, characterized in that, The ultrasonic power in step (1) is 100-1000W; And / or, the temperature in the ultrasonic reactor in step (1) is 15-90℃; And / or, in step (1), the residence time of the zinc salt solution, precipitant solution and cavitation aid in the ultrasonic reactor is 60-200 seconds.

5. The method for preparing zinc oxide as described in claim 1, characterized in that, The surface modifier in step (2) is a silane coupling agent; And / or, in step (2), the amount of surface modifier used is 3 to 20% of the mass of zinc oxide dispersion.

6. A zinc oxide, characterized in that, The zinc oxide is prepared by the method described in any one of claims 1-5, and the zinc oxide is in the hexagonal wurtzite crystal form, which can emit red light under 365 nm ultraviolet excitation. The average particle size of the zinc oxide is 60-1000 nm; The surface of the zinc oxide has oxygen vacancies, and the density of oxygen vacancies on the zinc oxide surface is 30-62%.

7. The zinc oxide as described in claim 6, characterized in that, The average particle size of the zinc oxide is 60-500 nm; And / or, the density of oxygen vacancies on the zinc oxide surface is 40-60%.

8. The use of zinc oxide as described in any one of claims 6-7 in sunscreen products.

9. A sunscreen product, characterized in that, The sunscreen product contains zinc oxide as described in any one of claims 6-7.

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